Yeah should have made the plenum bigger. Its the width of a T square.
Last year I did use the anemometer. I used the clean stock filter as a baseline. Then would partially block it with a Kleenex to replicate a dirty stock filter. Wind speed out the duct reduced much more than compared to the pleated filter.
What I did not test is a dirty pleated filter. But I barely use my AC. Only when it's super mega hot. Mostly to save on electrical costs.
I installed a 12v blower that blows in filtered outside air. I use that a lot to cool the trailer a little cheaper. Also works great boondocking since its 12v.
Come winter time I use it to blow in warmer air. Trailer stays freezing even after outside air starts warming up.
